package com.eatme.core.tree.bst.avltree;

import java.util.ArrayList;
import java.util.Random;

public class AVLTree<K extends Comparable<K>,V> {

    private class Node {

        private K key;

        private V value;
        private Node left,right;

        public int height;

        public Node(K key,V value) {
            this.key = key;
            this.value = value;
            left = null;
            right = null;
            height = 1;
        }

    }

    private Node root;

    private int size;

    public AVLTree() {
        root = null;
        size =0;
    }

    private int getHeight(Node node) {
        if (node==null)
            return 0;
        return node.height;
    }

    // 判断当前二叉树是否是一颗二分搜索树
    public boolean isBST() {
        ArrayList<K> keys = new ArrayList<>();
        inOrder(root, keys);
        for (int i = 0; i < keys.size(); i++)
            if (keys.get(i-1).compareTo(keys.get(i))>0)
                return false;
            return true;

    }

    // 判断该二叉树是否是一颗平衡二叉树
    public boolean isBalanced() {
        return isBalanced(root);
    }

    // 判断以Node为根的二叉树是否是一颗平衡二叉树,递归算法
    private boolean isBalanced(Node node) {
        if (node==null)
            return true;
        int balanceFactor = getBalanceFactor(node);
        if (Math.abs(balanceFactor)>1)
            return false;
        return isBalanced(node.left) && isBalanced(node.right);
    }

    private void inOrder(Node node, ArrayList<K> keys) {
        if (node==null)
            return;
        inOrder(node.left,keys);
        keys.add(node.key);
        inOrder(node.right,keys);
    }

    // 获得节点node的平衡因子
    private int getBalanceFactor(Node node) {
        if (node==null)
            return 0;
        return  getHeight(node.left) -getHeight(node.right);
    }

    // 向二分搜索树中添加新的元素(key,value)
    public void add(K key, V value) {
        root = add(root,key,value);
    }

    // 向以node为根的二分搜索树插入元素(key,value), 递归算法实现
    // 返回插入新节点后二分搜索树的根
    private Node add(Node node, K key,V value) {
        if (node == null) {
            size++;
            return new Node(key,value);
        } else if (key.compareTo(node.key)<0) {
            node.left = add(node.left,key,value);
        }else if (key.compareTo(node.key)>0)
            node.right = add(node.right,key,value);
        else // key.compareTo(node.key) == 0
            node.value = value;

        // 更新height
        node.height =1+Math.max(getHeight(node.left),getHeight(node.right));

        // 计算平衡因子
        int balanceFactor = getBalanceFactor(node);
//        if (Math.abs(balanceFactor)>1)
//            System.out.println("unbalanced : "+balanceFactor);

        // 维护平衡性
        // LL
        if (balanceFactor>1 &&getBalanceFactor(node.left)>=0)
            return rightRotate(node);
        // RR
        if (balanceFactor<-1 && getBalanceFactor(node.right)<=0)
            return leftRotate(node);

        // LR
        if (balanceFactor>1 && getBalanceFactor(node.left)<0) {
            node.left = leftRotate(node.left);
            return  rightRotate(node);
        }

        // RL
        if (balanceFactor<-1 && getBalanceFactor(node.right)>0) {
            node.right = rightRotate(node.right);
            return leftRotate(node);
        }

        return node;
    }

    // 对节点y进行向右旋转操作,返回旋转后新的根节点x
    //        y                                    x
    //       / \                                  / \
    //      x   T4      向右旋转(y)               z    y
    //     / \          ---------->            / \   / \
    //    z   T3                              T1 T2 T3 T4
    //  /   \
    // T1   T2
    private  Node rightRotate(Node y) {

        Node x = y.left;
        Node T3 = x.right;

        // 向右旋转过程
        x.right = y;
        y.left =T3;

        // 更新height
        y.height = Math.max(getHeight(y.left),getHeight(y.right))+1;
        x.height = Math.max(getHeight(x.left),getHeight(x.right))+1;

        return x;

    }
    // 对节点y进行向左旋转操作,返回旋转后新的根节点x
    //        y                                    x
    //       / \                                  / \
    //      x   T4      向左旋转(y)               y    z
    //     / \          ---------->            / \   / \
    //    z   T3                              T1 T2 T3 T4
    //  /   \
    // T1   T2
    private  Node leftRotate(Node y) {

        Node x = y.right;
        Node T2 = x.left;

        // 向右旋转过程
        x.left = y;
        y.right =T2;

        // 更新height
        y.height = Math.max(getHeight(y.left),getHeight(y.right))+1;
        x.height = Math.max(getHeight(x.left),getHeight(x.right))+1;

        return x;

    }


    // 从二分搜索树中删除元素键为key的节点
    public V remove(K key) {
        Node node = getNode(root,key);
        if (node != null) {
            root = remove(root,key);
            return node.value;
        }
        return null;
    }

    // @Override
    public boolean contains(K key) {
        return getNode(root,key)!=null;
    }

    // @Override
    public V get(K key) {
        Node node = getNode(root,key);
        return node == null ? null : node.value;
    }

    // @Override
    public void set(K key, V newValue) {
        Node node = getNode(root,key);
        if (node == null)
            throw new IllegalArgumentException(key +"doesn't exist.");
        node.value = newValue;
    }

    // @Override
    public int getSize() {
        return size;
    }

    // @Override
    public boolean isEmpty() {
        return size==0;
    }

    // 返回以node为根节点的二分搜索树中, key所在的节点
    private Node getNode(Node node,K key) {
        if (node == null)
            return null;
        if (key.compareTo(node.key)==0)
            return  node;
        else if (key.compareTo(node.key)<0)
            return getNode(node.left,key);
        else // key.compareTo(node.key)> 0
            return getNode(node.right,key);
    }

    // 返回以node为根的二分搜索树的最小值所在的节点
    private Node minimum(Node node) {
        if (node.left==null)
            return node;
        return minimum(node.left);
    }

    // 删除掉以node为根节点的二分搜索树中最小节点
    // 返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node) {
        if (node.left==null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }
        node.left = removeMin(node.left);
        return node;
    }

    // 删除以node为根的二分搜素树中键为key的节点,递归算法
    // 返回删除节点后新的二分搜索树的根
    private Node remove(Node node, K key) {
        if (node == null)
            return null;
        Node retNode;
        if (key.compareTo(node.key)<0) {
            node.left = remove(node.left,key);
            retNode = node;
        }else if(key.compareTo(node.key)>0) {
            node.right =remove(node.right,key);
            retNode = node;
        }else { // key.compareTo(node.key) == 0
            // 待删除节点左子树为空的情况
            if (node.left==null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                retNode = rightNode;
            }
            // 待删除节点右子树为空的情况
            else if (node.right==null) {
                Node leftNode = node.left;
                node.left = null;
                size--;
                retNode = leftNode;
            }else {// 待删除节点左右子树均不为空的情况

                // 找到比待删除节点大的最小节点,即待删除节点右子树的最小节点
                // 用这个节点顶替待删除节点的位置
                Node successor = minimum(node.right);
                successor.right = remove(node.right,successor.key);
                // size++;
                successor.left = node.left;

                node.left =node.right = null;
                // size--;
                retNode = successor;
            }
        }

        if (retNode==null)
            return null;

        // 更新height
        retNode.height =1+Math.max(getHeight(retNode.left),getHeight(retNode.right));

        // 计算平衡因子
        int balanceFactor = getBalanceFactor(retNode);

        // 维护平衡性
        // LL
        if (balanceFactor>1 &&getBalanceFactor(retNode.left)>=0)
            return rightRotate(retNode);
        // RR
        if (balanceFactor<-1 && getBalanceFactor(retNode.right)<=0)
            return leftRotate(retNode);

        // LR
        if (balanceFactor>1 && getBalanceFactor(retNode.left)<0) {
            retNode.left = leftRotate(retNode.left);
            return  rightRotate(node);
        }

        // RL
        if (balanceFactor<-1 && getBalanceFactor(retNode.right)>0) {
            retNode.right = rightRotate(retNode.right);
            return leftRotate(retNode);
        }
        return retNode;

    }

    public static void main(String[] args) {
        ArrayList<Integer> arrayList = new ArrayList<>();
        Random random = new Random();
        for (int i = 0; i < 100; i++) {
            arrayList.add(random.nextInt(100));
        }
        System.out.println(arrayList);
        System.out.println("arraylist size:"+arrayList.size());
        AVLTree<Integer,Integer> map = new AVLTree<>();
        for (int i = 0; i < arrayList.size(); i++) {
            if (map.contains(arrayList.get(i)))
                map.set(arrayList.get(i),map.get(arrayList.get(i))+1);
            else
                map.add(arrayList.get(i),1);

        }

        System.out.println("Total different numbers: " +map.getSize());

        System.out.println("Frequency of 0: " +map.get(0));
        System.out.println("Frequency of 1: " +map.get(1));
    }
}
